Generally, inkjet printers have a print cartridge which comprises an orifice plate having orifices through which droplets of fluid (e.g., ink) are expelled onto a medium (e.g., paper) to create a mark. Ink fluids generally contain colorant(s) which mark the paper by soaking into it. Because the paper absorbs this ink it may be subject to low optical density, low edge acuity, bleeding, and low durability (smudge fastness, light fastness, and water fastness).
One or more of these problems may be solved by the use of reactive inks. Many colorant molecules used in inkjet inks (e.g., dyes or pigments) are negatively charged (anionic) to make them soluble in aqueous vehicles. Generally, to mark a medium using reactive ink, a dye or pigment and a fixer are mixed on the medium. The dye or pigment and fixer react. Reactive inks may utilize a positively charged or cationic species in a separate solution (fixer) to neutralize the colorant on the surface of the medium and render it insoluble. Excess reactants, vehicle, or other reaction products may be absorbed into the medium. The deposited precipitates are no longer excessively water-soluble and this may greatly increase the waterfastness of the print. Resultant prints may also have higher optical density, higher edge acuity, higher durability, less color-to-color bleed, and may be less susceptible to smudging than non-reactive ink systems. Additionally, writing systems using reactive inks may provide print attributes that are less dependent on the properties of the media used.
When using reactive inks it may be advantageous to print the reactants in such a manner that they do not mix and react on, and possibly clog, the printhead. One way to limit the mixing of the reactants on the printheads may be to limit the physical proximity of the nozzles or orifices through which the reactants print. This may be done by printing the reactants from separate printheads having separate orifice plates or from separate orifice plates sharing a common substrate. Printing from separate orifice plates, while possibly alleviating the reaction of the reactants on the printheads, may still be susceptible to deposition of material onto and clogging of the printhead because of the aerosol action of the reactants. Separate printheads and/or orifice plates may also be undesirable because the printheads and orifice plates generally comprise a substantial portion of the cost of printer cartridges, because printer cartridge size is increased, and because two printheads may require more inefficient over-travel (additional distance on each side of the print swath that the carriage must travel in order for the end printhead to complete the printing of a full swath across the media).
To keep costs down and possibly improve efficiency by reducing the amount of over-travel, it may be desirable to print reactive inks from separate nozzles on a single orifice plate on a printhead. However, the closer the proximity of the nozzles which print the reactants, the greater the likelihood of mixing on and possible clogging of the printhead due, not only to aerosol action, but also, for example, to puddling of the liquids during printing or firing, mixing by wiping during printhead servicing, capping during storage, or during application or removal of protective tape from the printhead.
Accordingly, it may be desirable to design a system in which it is possible to print two reactants (e.g., a reactive ink and a fixer) from the same printhead onto a medium (e.g., paper) while minimizing the mixing on the printhead of the reactants and possible clogging of the printhead.